1. Field of the Invention
The present invention relates to an apparatus for hydraulically shaping hollow bodies of metal using a shaping tool arranged in a press frame.
2. Description of the Related Art
In a method known in the art for hydraulically deforming metal hollow bodies, particularly tubular structural components, by means of an internal high pressure, the hollow body is placed in an initially open two-part shaping tool composed of an upper part and a lower part, the shaping tool is then closed and to at least one end of the hollow body is then secured a sealing plug through which a hydraulic internal high pressure is applied to the hollow body in order to shape the hollow body in accordance with predetermined contours in the shaping tool.
This known method predominantly uses hydraulic holding presses with a stationary lower part and a displaceable upper part. The upper part is closed and opened by means of hydraulic cylinders. The holding press is controlled in such a way that it holds the shaping tool closed for a longer period of time during the hydraulic shaping process. The cylinders must travel the entire distance in accordance with the opening stroke. This results in correspondingly long cycle periods. Since the closing force required for the internal high pressure shaping process is relatively high, it is additionally required to provide a very complicated hydraulic system.
Also known in the art are presses in which the shaping tool is locked mechanically. Due to the forces acting during the hydraulic deformation and the resulting reaction forces, the side posts of the press frame may expand longitudinally with the result that the shaping tool opens. Consequently, the hollow body is no longer held in a positively engaging manner during the deformation in the plane of separation between the lower part and the upper part; this has a disadvantageous effect on the quality of the shaped product. This means that a resetting of the shaping tool during the shaping process is required which, however, cannot be carried out or can only be carried out using a complicated construction in the presses known in the art.